The iconic flat 6 format used throughout the air-cooled era received various modifications/improvements during its evolution, even early on in production of the 2ltr models, continuing throughout 70’s with the early 935’s, most of which was driven by Porsche’s racing department.
Most of the engine machining modifications EB offer are based on Porsche’s own evolutions, however like all of our work we have looked to enhance/optimise the processes to maximise the performance gains and deliver a reliable and repeatable service. Each process developed to use all the benefits of our advanced machining capabilities, which has a number of advantages particularly if carrying out the full suite of upgrades. All of which is backed by our ISO9001/14001 QC.
- Boat Tailing and Spiggot Bore Relief
- Piston Squirters
- Oil Bypass
- Head Stud Repair
- General Stud Repair
We also undertake any other stud repairs or cracks/damage to both Aluminium and Magnesium, including re-chromate of magnesium castings.
On receipt the casings are stripped of any studs/bearing shells etc, hot washed and typically vapour blasted followed by a full inspection.
The case halves are mounted to a fixture on our 5 axis CNC milling machine, where there Renishaw probed at numerous points including the spigot bores and deck heights. The data gathered is documented and shows any/all deviations from OEM specs, we also check for any warp or twist, particularly in the early Magnesium cases.
Boat Tailing & Spiggot Bore Relief
This is a modification the factory performed on early cases particularly the smaller 2ltr capacity to reduce windage/loses. The typical method involves removing the square outer face of the support webs by die grinding and hand dressing/finishing, although functional, the result can only be radiused which are often non-uniform.
Our process started by reverse engineering/CAD modeling the cases, this provided OEM data for not only the main works but any additional thread or casting repairs.
Using CAD data and CFD we developed a profile that optimises the flow over and around the webs at the same time carrying this across all the bores for uniformity. This process is only achievable using a 5-axis machining centre with the latest in CAM.
Whilst we were developing the Boat tailing process we also took the liberty of improving the shape of the spigot bores, removing unwanted material smoothing the flow. We believe this is a unique EB development and only achievable with our level of machining capabilities.
We typically perform the process to all 2ltr variants, 2.4, 2.7 and 3ltr cases.
Our process has become standard practice for leading engine builders, helping to achieve numerous podiums and championship wins
In the late 60’s the factory made the addition of squirters in the crankcase to spray oil onto the underside of the piston to help reduce temperatures, like most of the development this was originally performed on the competition cars.
It was our belief the factory optimised the geometry on the later 3ltr production case, so we took the decision to use this over the alternative. To allow the squirter to be correctly installed/seated for cylinder no. 4 it requires the oil gallery enlarging to feed the intermediate shaft, an advantage of performing the modification on our 5axis is it’s performed in a single Opp. often overlooked or negated by others due to multiple opps/fixtures on traditional machines.
This is a common addition for early sandcast 2ltr cases particularly those used in competition builds such as the 2ltr cup.
Early engines had the oil bypass system directing excess oil in to the crankcase for the scavenge to pick up and recirculate. In the later models’ greater demands were put on the lubrication system which led to excess oil sitting in the crankcase, not only affecting the lubrication system but creating drag which reduces performance.
The modification involves machining a passage to the oil pump intake and installing a plug into the original port outlet.
This is a common upgrade on early cases which can be performed as an independent process.
Early competition engines had reliefs machined into the skirt of the barrels/cylinders, often referred to as scallops to help reduce windage.
A simple modification that can be performed independently, however we have configured the scallop to match our spigot bore relief, performing the work on the 5 axis allows us to rotate barrel in B axis and machine on the side face of the cutter to provide a cleaner cut, improved corner radius and reduces the risk of chipping/flaking of the Nikasil coating.
Engine Machining Repair Examples
Here are some examples of the repair work we have undertaken, including thread repairs and casting repairs on both magnesium and aluminium engines.
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